Comments on status:The black-crowned night-heron has shown a dramatic history of decline with only 4 sizeable colonies remaining in Illinois *01*. This species was placed on the Illinois endangered species list in 1977 and remains qualified for inclusion because of a) past history of decline b) small population numbers, and c) essential habitats are being threatened *01*. This species is also protected under the Migratory Bird Treaty Act of 1918 and the Illinois Wildlife Code of 1971 *19,22*.

Comments on species-habitat associations:The black-crowned night-heron seems adapted to nearly every conceivable habitat in which a wading bird may exist *04*. This species depends on wetlands for food and is found near freshwater ponds, lakes, sluggish streams, swamps, marshes, backwaters and shallow lagoons *12,14*. The proximity of foraging areas might be the most important factor in nest site selection, therefore, black- crowned night-herons utilize a wide variety of upland and lowland tree species and where suitable tree species cannot be found they will often nest in marsh vegetation where their nests are concealed *03,05, 14*.

Important plant and animal association: Gizzard shad.Gizzard shad seem to be the principal food item of this species (and other herons) in Illinois *03,04,14*.

High value habitats

Habitat

Structural stage

Season

Forested wetland

Special habitat

Fall

Forested wetland

Special habitat

Spring/summer

Nonforested wetland

Special habitat

Fall

Nonforested wetland

Special habitat

Spring/summer

Wet-mesic upland forest

All

Fall

Wet-mesic upland forest

All

Spring/summer

Floodplain forest

All

Fall

Floodplain forest

All

Spring/summer

Wetland

Special habitat

Fall

Wetland

Special habitat

Spring/summer

Marsh

Special habitat

Fall

Marsh

Special habitat

Spring/summer

Swamp

Special habitat

Fall

Swamp

Special habitat

Spring/summer

Shrub swamp

Special habitat

Fall

Shrub swamp

Special habitat

Spring/summer

Lakes and ponds

Not applicable(HVAL-HAB cover)

Fall

Lakes and ponds

Not applicable(HVAL-HAB cover)

Spring/summer

Streams

Special habitat

Fall

Streams

Special habitat

Spring/summer

Marsh restoration

Special habitat

Fall

Marsh restoration

Special habitat

Spring/summer

Species-habitat interrelations: 1) Wetlands, foraging sites, high, spring/summer/fall *01,12,14*.2) Bottomland forest, forested wetlands, nesting sites, high, spring/summer *01,04*.The black-crowned night-heron's nesting sites are so varied, as to suggest the quality and proximity of foraging areas might be the most important factor in nest site selection *01,03,14*. Thus, this species frequents areas such as lagoons, backwaters, marshes, swamps, ponds, lakes, sluggish streams and rivers to secure a foraging site, consequently nesting in best available situation *01,03,05,07,13,14*.

Comments on feed-guilding:The black-crowned night-heron is a wading bird that eats primarily fish and other aquatic life. This species is extremely adaptable and eats whatever is most plentiful at the time and place. It is also known to take young birds and small mammals (mice) *03,05,07*.

Comments on breed-guilding:The black-crowned night-heron usually copulates at or near its nest site *04*. Usually places nest in trees, shrubs, or marsh vegetation near accessable foraging areas *00,01,03,04*.

Comments on food habits: General: The most important food item for the black-crowned night-heron in Illinois seems to be small fishes primarily gizzard shad *03,14*. This species has been reported to take some algae and other succulent plants, but it is classified as pre-eminently carnivorous *05,12*. The black-crowned night-heron is extremely adaptable and eats whatever is most plentiful at the time and place *07*.Juvenile: Juvenile food items seem identical to adult food items but are presented in different forms depending on age of young. At hatching, young are fed predigested juices and size of food increases with age of young *04,12*. See general or important food items.Adult: See general or important food items.

Comments on environmental associations:General: Foraging areas appear more critical to the black-crowned night-heron than nest sites *01*. Unpolluted and undisturbed wetlands are essential as foraging areas and considering the adaptability of this species it can nest in a variety of situations *01,03,04,14*.Feeding juvenile: Nestlings are fed in the nest and assumed to adopt adult feeding habits when fledged. See environmental assoc. for feeding adult *00*.Resting juvenile: Juveniles initially rest in nest and near nest site after fledging. They then move to roost trees with adults. Since this species is highly variable in the placement of its nest, resting areas may be located from near ground, in shrubs, vines, to a variety of tree species *03,04,05,13*.Feeding adult: Unpolluted, undisturbed wetlands are essential as foraging areas *01,03*.Resting adult: Adults may rest near nest site and in roost trees *07*. Due to highly variable nest placement this species may rest in a variety of shrubs, vines and trees, etc. *04*.Breeding adult: See species environmental associations and limiting factors. Also stability was seemingly critical to the selection of nest sites in North Carolina, Massachusetts and Virginia *08*. Birds will nest in any available vegetation that will support a nest *08*.

Physical description: 23-28 ins. in length; 45 in. wingspread. Sexes are outwardly similar but males average larger. Body is heavy, chunky; short thick neck, short legs and heavy bill. Adults: head with black cap, short crest. 2-3 Narrow white plumes at back of head. Eyes scarlet, back black, underparts white, wings and tail gray. Immature: brown streaked or spotted with white *04,07,21*.

Reproduction: The black-crowned night-heron is seasonally monogamous *04*. It is a colonial nester often nesting with other heron species, but also nests singly *03*. It is reported that Illinois birds go directly to their nesting colonies as they return from wintering *03*, but palmer (1962) states there is a definite delay before the occupying of nesting territory *04*. Courtship and mating are not described for Illinois *03*. Palmer (1962) reports both sexes arrive at approx. the same time. After a delay the male selects a territory and begins to display. As with the snowy egret the displaying male attracts a crowd, eventually letting 1 female in to nest *04,07*. Courtship is simple and once pair bond is formed it is maintained through the greeting display, billing and feather nibbling *04*. If the male chooses a territory containing an old nest the pair may rework this by adding new material. Typically the male brings the female sticks/twigs and she does the actual construction *04*. Unlike other heron species the male black-crowned night-heron rarely finishes the foundation (of a new nest) prior to pair formation *04*. The nest site of the black-crowned night-heron is highly variable ranging from ground level to over 160 ft. in a wide variety of upland and lowland trees, shrubs or aquatic vegetation *03,04,05*. This species will nest in any available vegetation that will support a nest *08*. The quality and proximity of foraging areas might be the most important factor in nest site selection *14*. Building material varies with habitat but generally consists of sticks/twigs or stems *04,07*. In New England it usually takes 2-5 days sometimes 7 days to complete nest construction *04, 05*. Copulation takes place in or near nest site and is typically preceeded by a greeting ceremony. Copulation usually occurs on 1st or 2nd day after pair formation. Duration averages 12 (8-17) seconds *04*. The first egg is layed on ave. 3.3 days after first copulation and 4-5 days after pair formation *04*. Nesting begins: Florida (Dec.); Georgia (mid Apr.); South Carolina (mid-late Apr.); New Jersey (early Apr.); New York (mid Apr.); Michigan (late Apr.-early May); Minnesota (late Apr.) *04*. Egg dates; north and central Illinois (24 Apr.-18 June); New England (May 13-20); California (May 3-23); New Jersey and Pennsylvania (Apr. 10-June 12); Florida (March 1-Apr. 17) *03,05*. Clutch size averages 3-5 (1-6) and rarely 7 or 8 eggs. The larger sets may be the product of 2 birds *04*. Mean clutch size apparently increases as move northward within the species range *08*. Mean clutch size also decreases as the season progresses. Apparently late nesters are usually young birds nesting for the first time and older individuals lay larger clutches *08*. Eggs are pale green-blue, 53 x 37 mm., and are apparently layed at 2 day intervals *03,04,05*. Incubation begins with the first egg and continues for 24-26 days. Both sexes incubate *04,05,07*. Upon hatching, young are partially covered with gray down with long whitish filaments on the crown *05*. The first day after hatching the young are fed pre-digested juices which are delivered into their open mouths *04,05*. After 3 days feeding consists of dropping larger pieces onto the floor or the rim of the nest and when older the young grab the parents bill in typical heron fashion *04,05*. Weights are approximately: 24.2 gm (1 day); 93.5 gm (5 days); 249.5 (10 Days); 598 gm (28 days) and 935 gm (44 days) *04,13*. First flight occurs at approximately 6 weeks usually to pursue adults to feeding areas to beg for food *04*. Young birds assume full adult plumage at approx. 2 1/2 years *05*. First year individuals were observed breeding in Rhode Island and New England but most usually not until 2-3 years *04,08,13*.

Behavior: The black-crowned night-heron is migratory spending from early Apr.-late Oct. in Illinois. This species breeds from Washington, Saskatchewan, Minnesota and New Brunswick south to South America and winters in the warmer parts of its range *01*. It is territorial on both nesting and feeding grounds *04*. On breeding grounds the male selects a territory that is used for hostile and sexual displays, copulation and nesting *04*. As with other heron species, initial territory of the male is larger than subsequent territory held by mated pair, which is little more than a few feet around nest *04*. The black-crowned night-heron engages in ritualized displays for threat, defense, and courtship *04*. The black-crowned night-heron is highly social and usually nests with other heron species, especially the great blue heron and great egret *04*. This species seems adapted to every conceivable habitat in which a wader may exist and it appears nest site selection revolves around the quality and proximity of foraging areas *14*. The black-crowned night-heron is an expert still-fisherman but also stalks its prey. Its periods of greatest activity are from dawn to sunrise and dusk until dark *05*. It is largely but not strictly nocturnal and sometimes feeds during daytime *07*. Most daylight hours are spent roosting in trees *07*. As in other herons, the black-crowned night-heron experiences a post-breeding dispersal, usually being the young birds that indulge in these erratic movements *03,04,05*. Northward flights begin in august soon after nesting is completed *03*. How soon southward flights begin is not known but suspect migration back through Illinois takes place Sept.- Oct. *03*. Though most of the population is south of Illinois by October there are enough Nov., Dec., and Jan. records to suggest that a few individuals linger, perhaps regularly *03*. The lack of Feb. records may mean poor winter survival or just a paucity of observers *03*.

Limiting factors: Population size for Illinois is not known but only 4 sizeable breeding colonies remain *03,17*. Numbers have been reduced in many localities by land clearing, drainage, lumbering, and development *01,04*. Black-crowned night-herons are susceptible to pollution. The presence of organochlorines and heavy metals are present in eggs taken from Mass., N.J., M.Y., Md., R.I., Conn., Va., N.C., S.C., Fla., Ga., Ohio, Mich., Wisc., and Minn. *18*. This study could not positively relate residues to declines of night-heron populations but circumstantial evidence suggests that environmental pollutants may contribute to impaired reproductive success in the more contaminated areas *18*. Enemies include raccoons, crows, hawks, vultures, skunks, weasels and foxes *05, 10,13*. Black-crowned night-herons are particularly sensitive to disturbance just before and during laying *06*. In Quebec, disturbance reduced nesting success by inhibiting laying, increasing either nest abandonment or egg predation and increased nestling mortality *06*. The filling and draining of wetlands and continued use of persistent pesticides reduce viable foraging areas that are essential to this species *19*. Preservation and proper care of both nesting and foraging areas are critical and human encroachment during breeding season should be eliminated in order to prevent decreased nesting success *01*.

Population parameters: The relative trend for the black-crowned night- heron in Illinois is not known. Only 4 sizeable extant colonies: Pontoon Beach, Barrington, Clear Lake and Lake Calumet remain in 1983 and all are associated with areas that still have marshes near by *03,17*. Mortality rates have been reported as 61% for 1st year birds and 31% in older birds (after 2nd August of life) *12*. In Georgia nesting success was reported to be 87%, percent eggs that were successful was 71% *22*. Nesting success for Long Island was 100% with 94% eggs hatching. In Maryland, Virginia and North Carolina hatching success was 77.2% with 91.4% of hatchlings living through their 15th day *08*. 1 Estimate for productivity was made for Illinois. Neal (1976) found 3.3 young per nest in Waukegan *03*. Henney (1972) estimated 2.0-2.1 night-heron young had to fledge per nesting female to maintain a stable population *08*. No recent data is available. Black-crowned night-herons are reported to be stable or increasing their numbers in Massachusetts, Rhode Island, and Long Island *08*. No sex ratios are reported for Illinois. Average age of black-crowned night-herons is approx. 2 years 11 months and the oldest bird was found in Ohio at 21 years 1 month, for Illinois the oldest bird is just over 14 yrs. *12*. Life expectancy is 1.8 years and after the first year of life it increases to 2.7 years *12*.

Comments on management practices:The filling and draining of wetlands and continued use of persistent pesticides constitute a serious threat to all wading birds *19*. The preservation and proper care of both nesting and foraging sites is critical to the black-crowned night-heron's continuation as a breeding bird in Illinois *01*. Sanctuaries are the best means of preserving habitat *19*. It is also important to locate extant colonies and protect them *03*. Human encroachment during the breeding season should be eliminated to prevent nest abandonment *01*. The black- crowned night-heron is protected as an endangered species in Illinois, by the Migratory Bird Treaty Act of 1918 and the Illinois Wildlife Code 1897 *01,19,22*.